Manual reset thermostat

ABSTRACT

A trip-free manual reset bimetal disc operated thermostat is disclosed. A unitary bumper operatively connects the disc to a pair of switches and a manual reset member. The travel of the manual reset member is limited, and the elements are proportioned so that full movement of the reset member does not cause switch operation unless the disc is at reset temperatures. The elements are arranged to cooperate to define a pair of switch chambers which are isolated from each other and are also isolated from a disc cavity.

United States Patent Place I [1 1 3,675,178 July4, 1972 MANUAL RESETTHERMOSTAT 3,219,783 11/1965 Odson ..337/348 sea 3,428,932 2/1969Manecke ..337/348 Primary ExaminerBemard A. Gilheany AssistantExaminerDewitt M. Morgan Attorney -McNenny, Farrington, Pearne & Gordon[57] ABSTRACT A trip-free manual reset bimetal disc operated thermostatis disclosed. A unitary .bumper oper'atively connects the disc to a pairof switches and a'manual reset member. The travel of the manual resetmember is limited, and the elements are proportioned so that fullmovement of the reset member does not cause switch operation unless thedisc is at reset temperatures. The elements are arranged to cooperate todefine a pair of switch chambers which are isolated from each other andare also isolated from a disc cavity.

17 Claims, 5 Drawing Figures Patented July 4, 1972 3,675,178

, 2 Sheets-Sheet l INVENTOR DOA/440 E. PZACZ BY /6 n A/a/A/x/mee/A/araPam/5 {604 M MANUAL RESET THERMOSTAT BACKGROUND or THE INVENTION Thisinvention relates generally to bimetal operated thermostats and moreparticularly to a novel and improved manual reset bimetallic discoperated thermostat.

PRIOR ART Manual reset bimetal disc operated thermostats are known.Examples of such thermostats are illustrated in the U.S. Pat. Nos.2,714,644; 3,164,702; and 3,428,932. The latter of these patentsdescribes a thermostat of this general type which may include eitherdouble pole or single pole switches and which may be trip-free" in thatthe reset mechanism is described as being arranged so that its operationcannot close the switch unless the disc has returned to a resettemperature.

SUMMARY OF THE INVENTION 7 A manual reset thermostat in accordance withthis invention provides improved reliability with a simplifiedstructure.

In the illustrated embodiment a double pole, double break switchmechanism is mounted in the body assembly in a symmetrical manner withrespect to the central axis of the bimetallic snap disc. A singleunitary bumper element engages the center of the disc and is providedwith lateral arms which engage and operate the switches. A reset memberis centrally mounted for movement along the central axis. When operated,the reset member engages the bumper and thereby moves the disc towardits reset position. Body stops limit the movement of the reset member toa position which does not cause the switches to close unless the dischas returned to reset temperatures. Therefore, operation of the resetdoes not result in switch closure if the disc remains above its resettemperature and the thermostat is trip-free. Further, the limited travelof the reset prevents damaging stresses from being applied to the disc.

Relatively stiff bridging contacts are provided in each switch.Consequently, they do not flex or elastically deform during operationand a reliable opening is provided even when contact welds occur. Thestructure is arranged so that the bridging contacts are retained inposition by cooperating surfaces provided on the body and reset memberand separate mounting or positioning means are not required. A springextends between each bridging contact and the reset member and performsthe dual function of urging the switches toward their closing positionand the reset member toward its normal retracted position.

The structure is arranged so that the cavity in which the disc islocated is completely isolated from the switch chambers, and the switchchambers are isolated from each other. Consequently, arc splatter or thelike is confined and cannot reach the separated cavities or chambers ofthe mechanism.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a preferredembodiment of a thermostat incorporating the present invention;

FIG. 2 is a section taken along 2-2 of FIG. 1;

FIG. 3 is a enlarged fragmentary section taken along 3-3 of FIG. 1;

FIG. 4 is an exploded perspective view of the bumper, the bridgingcontacts of the switches, and the reset member; and

FIG. 5 is an enlarged fragmentary broken section illustrating themechanism in a condition in which the reset member is fully depressedbefore the disc returns to a reset temperature with the reset positionof the disc illustrated in phantom.

DETAILED DESCRIPTION OF THE DRAWINGS The illustrated embodiment of thisinvention includes a symmetrically positioned projections I7, two ofwhich appear in the section of FIG. 2. The periphery of the disc ispositioned against a step at 18 formed in the retainer I2 around acentral recess 19 which provides clearance for the center portion of thedisc.

The snap disc 16 is dished so that it has two positions of stabilitybetween which its central portion moves with snap action when it reachespredetermined temperatures. The line of action of such snap movement isalong a central axis 30 of the thermostat. In FIG. 2 the disc isillustrated in its reset position and when it snaps through to itsopposite position of stability, it is considered to be in its operatedposition. The disc is manufactured so that it snaps from the resetposition to the ing temperature to normal environmental temperature.Consequently, it is necessary to manually move the disc from itsoperated position toward its reset position in order to reset thethermostat. The manner in which this is done while providing tion of thebumper is fonned with a cylindrical projection 23 body assemblyconsisting of a main body member 10, a cap member 11, both formed ofinsulating material such as a phenolic resin, and a disc retainer 12preferably formed of having a reduced diameter extension 24 engageablewith the center of the disc 16. Above the cylindrical portion 23, thebumper is provided with two oppositely extending projections 26 and 27which extend laterally from the central axis 30. The upper sides of theprojections 26 and 27 are rounded as best illustrated in FIG. 4, and thecentral portion therebetween is provided with an upper extension 28.Longitudinal guide projections 29 are provided on opposite sides of thebumper which fit into mating recesses formed in the body to assist inguiding the bumper for movement along the axis 30. The upper end of thebumper is provided with a projection 31 having a generally sphericalconfiguration.

The main body 10 on the side of the wall 13 opposite the disc cavity 14is formed with a pair of switch chambers 32 and 33on opposite sides of acentral wall 34 which is interrupted in its center part to receive thebumper 22. The adjacent end faces of the wall 34 are provided withmating recesses 36 to receive the projections 29 for positively guidingthe bumper for movement along the axis 30. The mating projections 29 and36 extend a substantial distance along the bumper to provide positiveguidance and to prevent the bumper from tipping laterally. This insuresthat the bumper reliably operates both switches. These mating groovesand projections also function to increase the length of the surfacesextending between the two switch chambers to prevent arcing between theswitches and to prevent arc splatter from passing from one chamber tothe other.

Similar switch mechanisms are provided in each of the switch chambers 32and 33. The switch mechanism in the chamber 32 is best illustrated inFIG. 2, and it should be understood that the following descriptionapplies equally to the switch located in the chamber 33. The switchmechanism includes two terminal elements 37 and 38 secured against theswitch side of the wall 31 by rivets 39 and 41, respectively. Theadjacent ends of the terminal elements 37 and 38 are provided withstationary or fixed contacts 42 and 43 respectively. A bridging contact44 is proportioned to connect the contacts 42 and 43 when it is inengagement therewith as illustrated in FIG. 2 and provide an electricalconnection between the terminals 37 and 38. The terminals 37 and 38 areshaped to extend out of the switch cavities and are provided withterminal metal. The main body member 10 is provided with a lateralscrews 46 for connection to external wiring circuits. The

bridging contacts are formed of relatively heavy gauge material toprevent them from bending or flexing when they are engaged' by thebumper. Therefore, substantially the entire kinetic energy of the massin motion of the disc and bumper is available to break any welds whichmay occur between the contacts. This structure, therefore, insures thatthe contacts will open with reliability.

A reset member 47 having a shape best illustrated in FIG. 4

is preferably molded of an insulating material such as aphenolic resinand is provided with opposed depending legs 48 proportioned to straddlethe central wall 34 and forming parallel surfaces 51 extending downalong the sides of the wall 34 in all positions'of the reset member 47.In fact, the legs 48 extend past the upper end of the bumper andcooperate with the bumper and central wall to insure effective isolationof the two switch chambers. The bottom wall 52 of the recess defined bythe legs 48 is engageable with the top surface 53 of the wall 34 on bothsides of the bumper to limit movement of the reset member in a directiontoward the disc beyond an actuated position illustrated in FIG. 5.

The upper end of the reset member 47 is formed with a cylindricalprojection 54 which projects into an opening 56 formed in the cap 1 l.The upper surface 57 around the projection 54 engages a wall 58 to limitmovement of the reset member in a direction away from the disc beyondthe retracted position of FIGS. 2 and 3. The interengagement between thewall 52 of the reset member and the top surface 53 of the central wall34 extends a substantial distance on both sides of the bumper,preferably beyond the edge of the projection 54. This insures exactpositioning of the reset member in its actuated position even when theoperating force is eccentrically applied to the projection 54.

A pair of depending projections 59 extend from the legs 48 along theassociated switch cavity beyond the ends of the as sociated bridgingelements 44 to longitudinally position the bridging'elements andcooperate with the lateral walls of the associated switch chambers 32 or33 to entrap the bridging elements in their ,proper position. A spring61 extends between each bridging element and the reset member andperforms a combined function of urging the reset member 47 toward itsretracted position and the associated bridging elements 44 toward theirassociated contacts 42 and 43. Guide openings 62 formed in the resetmember properly position the spring 61. I

When the disc 16 is in the reset position illustrated in FIGS. 2 and 3,each bridging element 44 engages its associated contacts and the twoswitches are closed. The bumper 22 is proportioned so that clearance isprovided either between the extension 24 and the disc 16, or between theprojections 26 and 27 and their associated bridging contacts 44 at thistime. Also, the projection 31 on the upper end of the bumper is spacedfrom the bottom wall 52 of the reset member. When the disc snaps throughfrom its reset position to its operated position, the bumper 22 is movedupwardly causing the projections 26 and 27 to engage the associatedbridging elements after the disc is in snap movement and to thereafterlift the bridging elements against the action of the springs 61 to openthe switches. The various elements are proportioned so that a spacingstill exists between the projections 31 and the wall 52, so long as thereset member remains in the retracted position.

Resetting of the thermostat is accomplished by pressing in on theprojection 54 to cause the reset member to move inwardly to the positionillustrated in FIG. 5. At this time, the upper surface 53 of the wall 34is engaged by the reset member wall 52 to prevent inward movement of thereset member beyond the illustrated actuated position. The variouselements are proportioned so that movement of the reset to the actuatedposition of FIG. causes the reset member to engage the bumper and movethe bumper in a direction causing movement of the disc from the operatedposition toward the reset position. v

The elements are sized, however, so that movement of the reset button isincapable of moving the disc all the way to its reset position or ofmoving the bumper a distance necessary to cause the bridging contactstoengage both of the associated fixed contacts 42 and 43. Consequently,the switches remain open unless the temperature of the disc has reacheda reset temperature at which such reset mo vement causes the disc tosnap on through to its reset position (illustrated in phantom in FIG.5). With this structure, the thermostat is trip-free in that thethermostat switches cannot be closed before the disc reaches resettemperature.

If, for some reason, the reset member is blocked in its actuatedposition, the thermostat automatically cycles in that the disc opens theswitches when disc operating temperature is reached and snaps back toits reset position allowing the switches to close when the disc returnsto reset temperatures. The projection 54 is proportioned so that it isrecessed slightly below the surface of the cap 11 even when the reset isin its retracted position. This reduces the likelihood of accidentalengagement of the reset member and reduces the likelihood of excessiveforces being applied to the reset mechanism.

With the illustrated simplified structure, a single unitary bumperfunctions to operatively connect the disc to both switches and the resetmember. Further, the structure is arranged so that the body assemblycooperates with the bumper and reset member to effectively isolate thetwo switch chambers from each other and from the disc cavity.Consequently, arc splatter is confined and reliable operation isprovided through larger numbers of cycles.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondisclosed and claimed herein.

I claim:

1. A thermostat comprising a body assembly, switch means in said bodyassembly including a fixed contact and a mobile contact movable into andout of engagement with said fixed contact, a bimetallic snap disc insaid body assembly having a central portion movable along a line ofaction with snap movement between an operated position and a resetposition, a unitary bumper in said body assembly having a first surfaceengageable with said disc and a second surface engageable with saidmobile contact, said bumper operating said switch means when said discmoves between said reset position and said operated position, a resetmember movable in said body toward and away from said disc between aretracted position and an actuated position, stop means including asurface of said body assembly engageable by a cooperating surface of thereset member preventing movement of said reset member toward said discbeyond said actuated position, said reset member including a faceengageable with a portion of said bumper upon movement of said resetmember to said actuated position when said disc is in said operatedposition, said reset member thereby causing movement of said bumpertowards said disc, such movement of said bumper producing movement ofsaid disc towards said reset position without causing said switch meansto close when said disc is not at a reset temperature.

2. A thermostat as set forth in claim 1 wherein said body assemblyincludes a central wall which cooperates with said bumper to separatetwo switch chambers, similar switch means are provided with one locatedin each switch chamber, and said wall and bumper are formed with matingguide surfaces which guide said bumper for movement along said line ofaction. I

3. A thermostat as set forth in claim 2 wherein said guide surfacesinclude a pair of projections on said bumper extending a substantialdistance in the direction of said line of action and a pair of matingrecesses forrnedin said central wall.

4. A thermostat as set forth in claim 2 wherein said bumper is formedwith opposed lateral projections extending into said switch chambers,each projection providing a surface engageable with an associated mobilecontact.

5. A thermostat comprising a body assembly, switch means in said bodyassembly including a fixed contact and a mobile contact movable into andout of engagement with said fixed contact, a bimetallic snap disc insaid body assembly having a central portion movable along a line ofaction with snap movement between an operated position and a resetposition, a unitary bumper in said body assembly having a first surfaceengageable with said disc and a second surface engageable with saidmobile contact, said bumper operating said switch means when said discmoves between said reset position and said operated position, a resetmember movable in said body toward and away from said disc between aretracted position and an actuated position, stop means preventingmovement of said reset member toward said disc beyond said actuatedposition, means engaged by said reset member upon movement of said resetmember to said actuated position when said disc is in said operatedposition, said engaged means causing movement of said bumper towardssaid disc, such movement of said bumper producing movement of said disctowards said reset position without causing said switch means to closewhen said disc is not at a reset temperature, said body assemblyincluding a central wall which cooperates with said bumper to separatetwo switch chambers, similar switch means located in each switchchamber, said wall and bumper having mating side surfaces which guidesaid bumper for movement along said line of action, said bumper havingopposed lateral projections extending into said switch chambers, eachprojection providing a surface engageable with an associated mobilecontact, said stop means being provided by a lateral surface on saidcentral wall which extends a substantial distance on opposite sides ofsaid bumper.

6. A thermostat as set forth in claim 5 wherein each switch meansincludes a pair of spaced fixed contacts, and said mobile contact is abridging contact engageable with said fixed contact to provide anelectrical connection therebetween.

7. A thermostat as set forth in claim 6 wherein said projections extendbetween the associated fixed contacts.

8. A thermostat as set forth in claim 7 wherein each switch meansincludes a spring extending between said bridging contact and said resetmember, said spring urging the associated bridging contact toward itsassociated fixed contacts and said reset member toward its retractedposition.

9. A thermostat as set forth in claim 8 wherein said reset member isprovided with depending projections extending along both sides of saidcentral wall, said depending projections cooperating with said bodyassembly to entrap said bridging contacts in proper position.

10. A thermostat as set forth in claim 9 wherein said dependingprojections extend along opposite sides of said central wall in allpositions of said reset member and cooperate to insure completeisolation of said switch chambers.

11. A thermostat as set forth in claim 10 wherein said body assembly isprovided with a lateral wall with an opening therein, said bumperextending through said opening with a close fit, said lateral wall andsaid bumper cooperating to isolate said disc from said switch means.

12. A thennostat comprising a body assembly, switch means in said bodyassembly including a fixed contact and a mobile contact movable into andout of engagement with said fixed contact, a bimetallic snap disc insaid body assembly having a central portion movable along a line ofaction with snap movement between an operated position and a resetposition, a unitary bumper in said body assembly having a first surfaceengageable with said disc and a second surface engageable with saidmobile contact, said bumper operating said switch means when said discmoves between said reset position and said.

operated position, a reset member movable in said body toward and awayfrom said disc between a retracted position and an actuated position,stop means preventing movement of said reset member toward said discbeyond said actuated position, means engaged by said reset member uponmovement of said reset member to said actuated position when said discis in said operated position, said engaged means causing movement ofsaid bumper towards said disc, such movement of said bumper producingmovement of said disc towards said reset position without causing saidswitch means to close when said disc is not at a reset temperature, saidbody assembly including a central wall which cooperates with said bumperto separate two switch chambers, similar switch means located in 7assembly is provided with a lateral wall with an opening therethrough,said bumper extending through said opening with a close fit, saidlateral wall and said bumper cooperating to isolate said disc from saidswitch means.

14. A thermostat comprising a body assembly having a central axis, abimetallic snap disc in said body assembly having a central portionmovable along said axis with snap action between a reset position and anoperated position, a pair of similar switches symmetrically mounted withrespect to said central axis on said body assembly, each switchincluding a contact movable to cause opening and closing of theassociated switch, an elongated unitary bumper mounted in said body formovement along said central axis, a reset member mounted in said bodyfor limited movement along said central axis between a retractedposition and an actuated position, one end of said bumper engaging saidcentral portion of said disc, the opposite end of said bumper beingengageable with said reset member when said reset member is in saidactuated position, said bumper being formed with a pair of lateralsurfaces each engageable with one of said contacts, movement of saiddisc between said reset and operated positions causing said bumper tooperate said switches after said disc is in snap movement, movement ofsaid reset member to said actuated position when said disc is in saidoperated position causing movement of said bumper toward said disc andthereby causing said bumper to move said disc toward said reset positionwithout causing operation of said switches so long as said disc is notat a reset temperature.

15. A thermostat as set forth in claim 14 wherein such movement of saidreset member to said actuated position when said disc is at a resettemperature causes said disc to move to said reset position and causesoperation of said switches.

16. A thermostat as set forth in claim 15 wherein said lateral surfacesof saidburnper are intermediate the ends thereof.

17. A thermostat as set forth in claim 15 wherein said body assembly,bumper and reset member cooperate to define isolated switch chamberseach of which encloses a switch and an isolated disc cavity whichencloses said disc.

I t l

1. A thermostat comprising a body assembly, switch means in said bodyassembly including a fixed contact and a mobile contact movable into andout of engagement with said fixed contact, a bimetallic snap disc insaid body assembly having a central portion movable along a line ofaction with snap movement between an operated position and a resetposition, a unitary bumper in said body assembly having a first surfaceengageable with said disc and a second surface engageable with saidmobile contact, said bumper operating said switch means when said discmoves between said reset position and said operated position, a resetmember movable in said body toward and away from said disc between aretracted position and an actuated position, stop means including asurface of said body assembly engageable by a cooperating surface of thereset member preventing movement of said reset meMber toward said discbeyond said actuated position, said reset member including a faceengageable with a portion of said bumper upon movement of said resetmember to said actuated position when said disc is in said operatedposition, said reset member thereby causing movement of said bumpertowards said disc, such movement of said bumper producing movement ofsaid disc towards said reset position without causing said switch meansto close when said disc is not at a reset temperature.
 2. A thermostatas set forth in claim 1 wherein said body assembly includes a centralwall which cooperates with said bumper to separate two switch chambers,similar switch means are provided with one located in each switchchamber, and said wall and bumper are formed with mating guide surfaceswhich guide said bumper for movement along said line of action.
 3. Athermostat as set forth in claim 2 wherein said guide surfaces include apair of projections on said bumper extending a substantial distance inthe direction of said line of action and a pair of mating recessesformed in said central wall.
 4. A thermostat as set forth in claim 2wherein said bumper is formed with opposed lateral projections extendinginto said switch chambers, each projection providing a surfaceengageable with an associated mobile contact.
 5. A thermostat comprisinga body assembly, switch means in said body assembly including a fixedcontact and a mobile contact movable into and out of engagement withsaid fixed contact, a bimetallic snap disc in said body assembly havinga central portion movable along a line of action with snap movementbetween an operated position and a reset position, a unitary bumper insaid body assembly having a first surface engageable with said disc anda second surface engageable with said mobile contact, said bumperoperating said switch means when said disc moves between said resetposition and said operated position, a reset member movable in said bodytoward and away from said disc between a retracted position and anactuated position, stop means preventing movement of said reset membertoward said disc beyond said actuated position, means engaged by saidreset member upon movement of said reset member to said actuatedposition when said disc is in said operated position, said engaged meanscausing movement of said bumper towards said disc, such movement of saidbumper producing movement of said disc towards said reset positionwithout causing said switch means to close when said disc is not at areset temperature, said body assembly including a central wall whichcooperates with said bumper to separate two switch chambers, similarswitch means located in each switch chamber, said wall and bumper havingmating side surfaces which guide said bumper for movement along saidline of action, said bumper having opposed lateral projections extendinginto said switch chambers, each projection providing a surfaceengageable with an associated mobile contact, said stop means beingprovided by a lateral surface on said central wall which extends asubstantial distance on opposite sides of said bumper.
 6. A thermostatas set forth in claim 5 wherein each switch means includes a pair ofspaced fixed contacts, and said mobile contact is a bridging contactengageable with said fixed contact to provide an electrical connectiontherebetween.
 7. A thermostat as set forth in claim 6 wherein saidprojections extend between the associated fixed contacts.
 8. Athermostat as set forth in claim 7 wherein each switch means includes aspring extending between said bridging contact and said reset member,said spring urging the associated bridging contact toward its associatedfixed contacts and said reset member toward its retracted position.
 9. Athermostat as set forth in claim 8 wherein said reset member is providedwith depending projections extending along both sides of said centralwall, said depending projections cooperating with said body assembly toentrap said bridging contacts in proper position.
 10. A thermostat asset forth in claim 9 wherein said depending projections extend alongopposite sides of said central wall in all positions of said resetmember and cooperate to insure complete isolation of said switchchambers.
 11. A thermostat as set forth in claim 10 wherein said bodyassembly is provided with a lateral wall with an opening therein, saidbumper extending through said opening with a close fit, said lateralwall and said bumper cooperating to isolate said disc from said switchmeans.
 12. A thermostat comprising a body assembly, switch means in saidbody assembly including a fixed contact and a mobile contact movableinto and out of engagement with said fixed contact, a bimetallic snapdisc in said body assembly having a central portion movable along a lineof action with snap movement between an operated position and a resetposition, a unitary bumper in said body assembly having a first surfaceengageable with said disc and a second surface engageable with saidmobile contact, said bumper operating said switch means when said discmoves between said reset position and said operated position, a resetmember movable in said body toward and away from said disc between aretracted position and an actuated position, stop means preventingmovement of said reset member toward said disc beyond said actuatedposition, means engaged by said reset member upon movement of said resetmember to said actuated position when said disc is in said operatedposition, said engaged means causing movement of said bumper towardssaid disc, such movement of said bumper producing movement of said disctowards said reset position without causing said switch means to closewhen said disc is not at a reset temperature, said body assemblyincluding a central wall which cooperates with said bumper to separatetwo switch chambers, similar switch means located in each switchchamber, said wall and bumper having mating side surfaces which guidesaid bumper for movement along said line of action, said reset memberincluding depending projections extending along both sides of saidcentral wall in all positions of said reset member, said dependingprojections cooperating with said body assembly and bumper to isolatesaid switch chambers.
 13. A thermostat as set forth in claim 12 whereinsaid body assembly is provided with a lateral wall with an openingtherethrough, said bumper extending through said opening with a closefit, said lateral wall and said bumper cooperating to isolate said discfrom said switch means.
 14. A thermostat comprising a body assemblyhaving a central axis, a bimetallic snap disc in said body assemblyhaving a central portion movable along said axis with snap actionbetween a reset position and an operated position, a pair of similarswitches symmetrically mounted with respect to said central axis on saidbody assembly, each switch including a contact movable to cause openingand closing of the associated switch, an elongated unitary bumpermounted in said body for movement along said central axis, a resetmember mounted in said body for limited movement along said central axisbetween a retracted position and an actuated position, one end of saidbumper engaging said central portion of said disc, the opposite end ofsaid bumper being engageable with said reset member when said resetmember is in said actuated position, said bumper being formed with apair of lateral surfaces each engageable with one of said contacts,movement of said disc between said reset and operated positions causingsaid bumper to operate said switches after said disc is in snapmovement, movement of said reset member to said actuated position whensaid disc is in said operated position causing movement of said bumpertoward said disc and thereby causing said bumper to move said disctoward said reset position without causing operation of said switches solong as said disc is not at a reset temperature.
 15. A thermostat as sEtforth in claim 14 wherein such movement of said reset member to saidactuated position when said disc is at a reset temperature causes saiddisc to move to said reset position and causes operation of saidswitches.
 16. A thermostat as set forth in claim 15 wherein said lateralsurfaces of said bumper are intermediate the ends thereof.
 17. Athermostat as set forth in claim 15 wherein said body assembly, bumperand reset member cooperate to define isolated switch chambers each ofwhich encloses a switch and an isolated disc cavity which encloses saiddisc.